Short bowel syndrome and GLP-2

Short bowel syndrome (SBS) is what happens when so much small intestine has been removed or lost that what remains cannot absorb enough food, fluid and salts. It usually follows surgery: for Crohn's disease, for a blocked blood supply to the gut, for a twisted bowel, after trauma, or in newborns after conditions such as necrotising enterocolitis. Some people adapt with diet and medicines. Others need nutrition or fluid through a vein, sometimes for life.

Who has it

The adult teduglutide trials give a sense of the population. In the 85 patients analysed in the pivotal STEPS study, the mean age was 50 and people had depended on intravenous support for a mean of 6 years (range 1 to 26). The commonest causes of short bowel were vascular disease (34%), Crohn's disease (21%) and other causes (21%). A stoma was present in 45%, most often a jejunostomy or ileostomy. Those details matter for the drugs, because whether the colon is still connected changes how much a GLP-2 analogue can add.

Intestinal failure

The European Society for Clinical Nutrition and Metabolism (ESPEN) defines intestinal failure as "the reduction of gut function below the minimum necessary for the absorption of macronutrients and/or water and electrolytes, such that intravenous supplementation is required to maintain health and/or growth". Short bowel syndrome is the most common cause of chronic intestinal failure in adults. When trial papers write SBS-IF, they mean short bowel syndrome severe enough to need intravenous support.

That support is called parenteral support, PS for short. It covers parenteral nutrition (calories, protein and fat into a vein) and intravenous fluids and electrolytes. It is usually infused overnight through a central line, several nights a week. It keeps people alive, and it brings its own risks: line infections, clots and liver problems linked to long-term intravenous feeding. The burden is measured in litres and nights. In the teduglutide STEPS trial, participants started on about 13 litres a week.

Where GLP-2 comes in

After surgery the remaining bowel adapts: the lining thickens, the villi lengthen and absorption improves. GLP-2 is one of the signals that drives that process. The problem is where it comes from. L cells, which make GLP-2, are concentrated in the terminal ileum and the colon, the parts most often removed. In a 2001 Copenhagen study, patients with no terminal ileum and no colon had no rise in GLP-2 after eating. Giving them GLP-2 for 35 days improved absorption of energy, wet weight and nitrogen, and increased villus height in six of eight.

So GLP-2 drugs are, in part, replacing a gut peptide that surgery took away. That also explains why the benefit is largest in people with an end stoma and smaller in people who still have their colon connected, as seen in the apraglutide STARS trial.

How trials measure success

GLP-2 trials do not measure weight loss or blood glucose. They measure how much intravenous support people can safely give up. The rules for cutting support are written into the protocol. In STEPS and EASE-1, for example, support was reduced when a 48-hour urine collection exceeded baseline by at least 10%, meaning the gut was now absorbing more fluid.

Why the placebo groups improve

Placebo arms in these trials always lose some support: 2.3 litres a week in STEPS, 2.85 in EASE-1, 12.5% in STARS. Part of that is the protocol itself. Joining a trial means closer fluid monitoring and a systematic attempt to wean, and some people were on more support than they needed. That is why the difference between groups is the number to watch, and why a responder rate of 30 to 40% on placebo is normal in this field.

Reading results across drugs

The three GLP-2 analogues were tested in different trials with different populations, durations, weaning rules and primary endpoints. STARS reports percentages; STEPS and EASE-1 report litres and responders. No head-to-head trial exists. The safest reading is that each has shown more support reduction than placebo in its own trial, and that injection frequency (daily, twice weekly, once weekly) is the most visible practical difference.

The trade-off

The reason these drugs work, growth of intestinal tissue, is also the reason for their main warning. The teduglutide label requires colonoscopy before starting, after one year and at least every five years, and checks of bilirubin, alkaline phosphatase, lipase and amylase at least every six months. As absorption improves, intravenous volumes have to be reduced in step, or fluid overload follows. GLP-2 treatment is decided and supervised by an intestinal failure team.

The what is GLP-2 page covers the biology, and GLP-2 vs GLP-1 explains why none of this overlaps with weight loss drugs.

What to log

Intestinal failure care runs on numbers: intake, output, weight, nights on support and lab trends. Peptide AI's nutrition tracking, dose log and bloodwork tracking keep those on one timeline that is easy to share with the team.